Assembling a large scale wind turbine generator comprises the installation of a rotor in stator.
For a PM wind turbine generator of large scale, excessive magnetic forces will interact between magnets of the rotor and iron of the stator resulting in a complicated installation setup.
Disclosed in Danish patent DK 172430 is a method for assembling an electrical PM machine comprising a plurality of poles by first assembling said machine with a rotor established in the stator where said rotor is without mounted permanent magnets and secondly establishing said pre-magnetized permanent magnets in the rotor by mounting pre-magnetized permanent magnets in prepared slots comprised in the rotor.
A disadvantage by the described method is that at the installation extensive magnetic forces act between the magnets and other magnetic components of the electrical machine. This requires special precautions to be taken during installation comprising special tools for holding, lifting and handling the magnets, magnetic components and the forces that interact between them. Furthermore in the case of large scale machines, personel safety has to taken into account.
It is an object of the invention to provide technique without the above mentioned disadvantages and especially it is an object to provide technique that excludes the requirement of specialized tools specific for the transportation and installation of large magnetized magnets in a rotor.